This invention relates to a process of preparing para phenylenediamines, such as p-aminodiphenylamine.
Para phenylenediamines find a variety of utilities depending upon the para substituent. As an example, p-aminodiphenylamine is an important intermediate in the synthesis of rubber antioxidants and antiozonants. Other p-phenylenediamines, particularly C.sub.5-10 alkyl-substituted derivatives thereof, are also useful in stabilizing rubbers.
The syntheses of para phenylenediamines vary depending upon the para substituent and often require several steps which add undesirably to the production costs.
It would be advantageous to have a general, one-step process to produce para phenylenediamines. It would be more advantageous if the process did not produce significant quantities of undesirable by-products and intermediates, such as nitrosamines. It would be even more advantageous if the process did not use a liquid acid catalyst, since such a catalyst requires neutralization which leads to a waste salt stream. It would be most advantageous if the process employed a heterogeneous catalyst, so that the separation of the catalyst from the product stream is simple and inexpensive. With these multiple advantages, the process would be amenable to commercial application.